I find using fields works pretty well, but when I'm counting on my coworkers to (a) fill them in correctly and (b) not backspace/delete the controls out, I get a little frustrated. You might want to make sure everyone goes into their Options/Advanced? and under "Show document content" make sure Field Shading is set to "Always."

I do like the simplicity of the user getting a little user form popup at the start in which to fill those major variables - name, address, title, whatever else is pertinent. That way they should all go into the repeated form fields just fine. This is a rather simple visual tutorial: https://www.youtube.com/watch?v=slTDxIWvND0&t=471s

The other thing I would suggest is that you maybe ponder a bit about whether you need a few different templates. Based on this: "Section 1 might have five basic service options and the user deletes the four that don't apply." If what's really common is that you have projects that either span all five service options, or mostly just #1, then have a template ready to go that is just #1. That of course only works if the writer is clear on what the project entails when he/she starts writing the report. I work with engineers, and usually they have a good foundation on what the project requires, but in the process of working, they may need to insert sections for additional analysis or do additional testing, so usually they copy/paste sections or paragraphs in.